It is well known to ablate body tissue using a microwave applicator which heats and destroys the surrounding tissue. One use of such an applicator is in the non-invasive treatment of cancer in an internal body organ such as the liver. GB2415630 discloses an applicator of the above-mentioned type comprising a probe having a thin elongate shaft which can be inserted into the patient for treatment. The proximal end of the probe comprises a handle which is connected to an external microwave generator by an elongate flexible cable. A thin elongate microwave transmission line extends inside the probe from the handle to a radiating tip or antenna disposed at or adjacent the distal end of the probe. In use, the microwave field radiated from the tip heats and ablates the surrounding tissue in a localised area.
A disadvantage of the above-mentioned applicator is that the probe can heat up for a variety of reasons. Firstly, power losses can occur in the transmission line extending along the probe to the tip, which power losses heat the transmission line and the surrounding parts of the probe. Secondly, the radiated microwave energy can heat the probe. Thirdly, the heat from the ablation can be conducted back along the probe. Such heating of the probe is undesirable, since it can burn the patient's skin at the point of entry of the probe or it can burn other parts of the patient's body adjacent the shaft of the probe: for this reason UK government regulations specify that no external part of any medical apparatus should exceed 48° in temperature.
In order to overcome the above-mentioned problems, it is known to pass a liquid, such as a saline solution, along the probe of the applicator so as to cool the probe. One such applicator is disclosed in our co-pending International Patent Application No. PCT/GB2009/050113 filed 5 Feb. 2009, the contents of which are incorporated herein by reference, and comprises a probe having a pair of flow channels extending longitudinally along its shaft parallel to the transmission line, the channels being interconnected at the distal end of the shaft adjacent the radiating tip. In use, cooling fluid can be pumped through the probe to its distal end along one flow channel and then returned along another flow channel. A pair of flexible ducts extend from a handle of the probe and respectively allow the fluid flow into and out of the channels.
It will be appreciated that the flow channels have a very small diameter and hence and object of the present invention is to provide a pump which can create a sustained and reliable fluid flow through these channels that sufficiently cools the shaft of the probe.
Microwave applicator probes are generally single-use disposable items due to the fact that they cannot be reliably cleaned and sterilised following insertion into the human body. Also, since there is a risk that fluid flowing through the probe inside the body could become contaminated, it will be appreciated that both the fluid and the ducts carrying the fluid into and out of the probe need to be discarded following use. A problem with this is that the fluid also comes into contact with the pump and thus there is a risk that the fluid will contaminate the pump either directly or by virtue of the fact that there is a direct path for contaminants to travel back to the pump along the duct which connects it to the probe. Whilst pumps are difficult to clean and sterilise, they are too expensive to be discarded after each use. Accordingly, another object of the present invention is to provide a pump which overcomes this problem.
We have now devised a medical device which meets the above needs and objectives and which can be used in the treatment, therapy or diagnosis of the human or animal body.